Conventionally, there are demands for prevention of a peep at a mobile terminal such as a mobile phone from the perspective of privacy protection. Given such demands, various peep prevention techniques have been proposed. Such a peep prevention technique is exemplified by a technique using a viewing angle characteristic of liquid crystal.
Patent Literature 1 discloses a technique for switching between a wide viewing mode and a narrow viewing mode in a liquid crystal display device which causes a liquid crystal display to display an image. The wide viewing mode causes a display surface to be viewed at a wide viewing angle, whereas the narrow viewing mode causes the display surface to be viewed at a narrow viewing angle.
According to the technique, in the wide viewing mode, an identical image is seen on the display surface when the display surface is viewed either from the front or obliquely. In contrast, in the narrow viewing mode, an image (a main image) similar to the image seen in the wide viewing mode is seen when the display surface is viewed from the front, whereas a composed image obtained by composing a sub image which is completely different from the main image is seen when the display surface is viewed obliquely. This enables a user who wishes to protect privacy to prevent a peep by causing the display surface to be viewed in the narrow viewing mode.
Patent Literature 2 discloses the following technique. According to the technique, liquid crystal molecules in a pixel are aligned in two or more directions, so that a display panel has different transmittances when viewed from a vertical direction with respect to the display panel and when viewed from a direction which deviates from the vertical direction. This blurs an image which is seen by an observer located in a direction other than the vertical direction.
Patent Literature 3 discloses a technique for making it difficult to recognize an image or voice output state when a device detects a user who is different from a user who has logged in to the device.
Japanese Patent Application Publication, Tokukai, No. 2009-222943 (Publication Date: Oct. 1, 2009)
Japanese Patent Application Publication, Tokukai, No. 2009-64025 (Publication Date: Mar. 26, 2009)
Japanese Patent Application Publication, Tokukai, No. 2008-283578 (Publication Date: Nov. 20, 2008)